Evelyn M. Hickson, RN, MSN, CNS, WCC

Objectives

Describe the physiological changes that occur during pregnancy.

Identify changes in the lab values that occur during pregnancy as a result of normal physiological adaptation.

Identify abnormal laboratory values for the pregnant woman and the underlying physiology.

The most obvious changes in pregnant women are physical.

Fetal growth and enlargement of the uterus causes the rearrangement and compression of most abdominal organs.

Physical Physical ChangesChanges

45-50% increase in blood volume and cardiac output by term This contributes to the hyper-coagulability of

pregnancy and an increased risk of DVT due to increased clotting factors present in plasma.

Hypertrophy of both atria in the heart Common to auscultate dysrthymias or

murmurs Heart rate increases 8-15 bpm above

baseline

Late in pregnancy the inferior vena cava is completely occluded in the supine position. Cardiac output is highest in lateral and knee-chest

position. Prior to 24 weeks the effect of supine position is not

observed. Blood pressure

Decrease occurs by 8 weeks and into the second trimester and then gradually returns to nearly pre-pregnant level by end of the third trimester.

Non-pregnant = 35 ml/min 10 weeks = 50 ml/min 28 weeks = 125 ml/min Term = 500 – 1000 ml/min By the end of pregnancy 1/6th of

total maternal blood volume is contained in the vascular system of the uterus

Kidney and ureters Dilation more prominent on right. May last up to 3 months postpartum. Increased risk of pyleonephritis.

Bladder Decreased tone and increased capacity Displaced in late pregnancy Increased risk of UTI

Renal blood flow increases 35 – 60% Increase GFR results in excretion of glucose,

urea, uric acid, & calcium

Mechanical changes Enlarging uterus pushes on diaphragm and

compresses the space available for respiration

Biochemical changes Progesterone and Relaxin relaxing the

smooth muscles, joints and cartilage. The physiological dyspnea results in

hyperventilation , lower pCO2, and maternal respiratory alkalosis.

The lower pH facilitates the release of oxygen from mother to fetus.

Estrogen causes increased blood flow to the mouth, making the gums friable and contributing to gingivitis. The saliva becomes more acidic.

The tone of the lower esophageal sphincter decreases due to progesterone, causing smooth muscle relaxation, increasing heartburn and reflux.

Gastrointestinal Compression of abdominal organs and

hormonal changes lead to delayed gastric and intestinal emptying and increasing flatulence.

Cholestasis and cholelithiasis of pregnancy

Changes in pigmentation occurring in up to 90% of pregnancies Chloasma (mask of pregnancy) Linea nigra

Darkening of areola, umbilicus, vulva, and perianal skin.

Pigmented nevi, freckles and recent scars may deepen in color.

Sweat glands become hyperactive

Skin changes

Pruitic Urticaric Papules and Plaques of Pregnancy (PUPPS)

Mild degrees of hirsutism are common during pregnancy.

During normal pregnancy the proportion of hair in the growth phase is increased compared to that in the rest phase. After delivery, the number of hairs

entering the rest phase increase and it is normal to see a marked increase in scalp hair loss 2 to 4 months after delivery.

The breasts begin to change early in pregnancy, with tenderness, tingling sensations, and a feeling of heaviness within 4 weeks of the last menstrual period.

The breasts rapidly enlarge with ductal growth stimulated by estrogen and alveolar hypertrophy stimulated by progesterone.

Colostrum is present as early as 16 weeks.

Increased thickness of cornea Decreased intraocular pressure Common for prescriptions to change

during pregnancy, sometimes for the better.

Lordosis - Progressive increase in anterior convexity of the lumbar spine. Changes in the center of gravity

occur due to the shifting of weight and growth of the fetus.

Ligaments of the pubic symphysis and sacroiliac joints loosen and those suspending the uterus lengthen during pregnancy

Normal values for a non-pregnant adult woman Hct 36-48 and Hgb 12-16

During pregnancy the lower limits of normal Weeks Hgb Hct

12 11.0 33.3

16 10.6 32.0

20 10.5 32.0

24 10.5 32.0

32 11.0 33.0

36 11.4 34.0

40 11.9 36.0

Thyroid Function Test

Non-pregnant(microgram/dl)

Pregnant

Total T4 4.6-12 Increased

Total T3 80-180 Increased

TSH, Free T4, & Free T3 Unchanged

ABG Component Non-pregnant Pregnant

pCO2 (mmHg) 35-45 28-32

Bicarb (mEq/L) 22-25 18-31

pH 7.35-7.45 7.4-7.45

pO2 (mmHg) 75-100 95-105

SaO2 95-100% 95-100%(unchanged)

BE (mmol/L) -2 to +2 -2 to +2(unchanged)

ABG Component Non-pregnant Pregnant

WBC 5,000-10,000 5,000-15,000Increased to 20,000

in labor

RBC 5-6.25 4-5

Hgb 11.8-14.7 9.8-12.7

Hct 36-46% 32-36%

Plt 150,000-400,000/mm3

Unchanged until increase 3-5 days pp

Chemistry Non-pregnant Pregnant

Glucose 64-128 mg/dl No change

BUN, serum 10-20 mg/dl 5-12 mg/dl

Creatinine, serum 0.8-1.4 mg/dl 0.3-0.7 mg/dl

Uric acid, serum 3.5-9.0 mg/dl 1.2-4.5 mg/dl

Sodium, serum 136-144mEq/L 130-140mEq/L

Potassium, serum 3.7 to 5.2mEq/L 3.5-5.0mEq/L

Chloride, serum 101-111mEq/L 98-106mEq/L

Calcium 8.5-10.6 mg/dl Decreased 10%

Total protein 6.3-7.9 g/dl 5.5-7.5 g/dl

Albumin 0.5-4.5 mg/dl 3.0-5.0 g/dl

Globulin-A/G ratio 0.5-4.5 g/dl 3-4 g/dl

Bilirubin, total 0.2-1.9 mg/dl No change

Alk phosphatase 44-147 IU/L Inc until 6 wk pp

CO2 20-29 27-32

Bicarb 22mEq/L 21-30mEq/L

Cholesterol <200 mg/dl Up to 300 mg/dl

Urine Non-pregnantPregnant

Protein <150 mg/dl <300 mg/dl

Creatinine Clearance 91-130 ml/min 120/160 ml/min

American Thyroid Association. (2005). Thyroid disease and pregnancy. Retrieved February 23, 2005 from http://www.thyroid.org/patients/brochures/Thyroid_Dis_Pregnancy_broch.pdf.

Gabbe, S.G., Niebyl, J. R., Simpson, J. L., Senkarik, M., & Cooley, M. (Eds.). (2001). Obstetrics: Normal and Problem Pregnancies (4th ed.). New York:  Churchill Livingston

Varney, H., Kriebs, J.M. & Gegor, C. (2004). Varney's Midwifery (4th ed.). Boston:  Jones and Bartlett

Inturrisi, M. (ed.). (2003). Labor & Delivery In My Pocket: An Emergency Reference (2nd ed.). Mesa, AZ:  In My Pocket Books, Inc.

Somani, S., Bhatti, A., Ahmed, I.K. (2008). Pregnancy, Special Considerations. Retrived February 23, 2010 from http://emedicine.medscape.com/article/1229740-overview.